1. Field of the Invention:
The present invention relates to an oral composition comprising a fluoride compound. More particularly, it relates to an oral composition which is effective for prevention of dental caries because it permits a fluoride compound contained therein to maintain its stability for a long period of time and to give a high uptake of fluoride to the tooth enamel.
2. Description of the Prior Art:
It has been common practice to inhibit dental caries by using an oral composition such as dentifrice with a fluoride compound such as sodium fluoride, sodium monofluorophosphate, and stannous fluoride, contained therein which permits uptake of fluoride by tooth enamel for tooth reinforcement.
It is soluble fluoride dissolved in the composition that effectively acts on the tooth enamel. A fluoride compound initially incorporated into the composition may react with other ingredients in the composition to become insoluble. In this case, the amount of effective soluble fluoride decreases in the composition and the amount of fluoride for uptake by the tooth enamel will also decrease.
Usually a dentifrice contains calcium secondary phosphate, calcium carbonate, or aluminum hydroxide as an abrasive. When a dentifrice containing such a calcium-based or aluminum-based abrasive is incorporated with sodium fluoride or stannous fluoride, the fluoride ions react with calcium ions or aluminum ions liberated from the abrasive. This reaction forms insoluble CaF.sub.2 or AlF.sub.3 and deactivates the fluoride compound incorporated in the composition. This disadvantage is overcome to some extent when a monofluorophosphate is used as a fluoride compound; but deactivation is still inevitable where the storage period is long.
There has been a demand for a new abrasive to place the calcium-based or aluminum-based abrasives which are poor in miscibility with a fluoride compound. The new abrasive is required to be miscible with a fluoride compound, have good cleaning power, taste, and storage stability so that it would be suitable for use in oral compositions such as dentifrice.